CVE-2026-88778 — TCP Initial Sequence Number (ISN) prediction
Predictable exact value from previous values vulnerability in Citrix NetScaler ADC and Citrix NetScaler Gateway. This issue affects ADC: before 14.1-73.37, before 13.1-64.23, before 14.1-73.37 FIPS, and before 13.1.37.279 FIPS and NDcPP; Gateway: before 14.1-73.37 and before 13.1-64.23.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- Technical severity (high)+6
- Automatable exploitation (SSVC)+3
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Citrix Netscaler Application Delivery Controller, Citrix Netscaler Gateway, Citrix NetScaler ADC…).
- The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
- No fix documented in the sources: reduce exposure and monitor the vendor advisory.
- Search available logs for exploit probes, errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Citrix | Netscaler Application Delivery Controller | ≥ 13.1 and < 13.1-64.23≥ 13.1 and < 13.1.37.279≥ 14.1 and < 14.1-73.37≥ 14.1-66.68 and ≤ 14.1-73.37 | Vulnerable | NIST National Vulnerability Database |
| Citrix | Netscaler Gateway | ≥ 13.1 and < 13.1-64.23≥ 14.1 and < 14.1-73.37 | Vulnerable | NIST National Vulnerability Database |
| Citrix NetScaler | ADC | < 14.1-73.37< 13.1-64.23< 14.1-73.37 FIPS< 13.1.37.279 FIPS and NDcPP | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Citrix NetScaler | Gateway | < 14.1-73.37< 13.1-64.23 | Vulnerable | CVE Program (cve.org) e CISA ADP |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 8.8 | CVSS 4.0 | High | — | — | 50a63c94-1ea7-4568-8c11-eb79e7c5a2b5 via NIST National Vulnerability Database |
| 8.8 | CVSS 4.0 | High | — | — | NetScaler via CVE Program (cve.org) e CISA ADP |
| 7.5 | CVSS 3.1 | High | 3.9 | 3.6 | nvd@nist.gov via NIST National Vulnerability Database |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N (score shown at the top: nvd@nist.gov) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · citrix netscaler/adc, citrix netscaler/gateway
- SSVC assessment updated
- Record published
- CVSS changed · 7.5
- Source status changed · → Analyzed
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× Official description updated · Oct 15, 2026 – Oct 15, 2026
References
1 on the record
Elsewhere on this site
Related CVEs (same products)
- High CVE-2026-88779 Citrix NetScaler Improper Restriction of Operations within the Bounds of a Memory Buffer Vulnerability KEV 11d
- High CVE-2026-88774 Feature policy bypass due to improper HTTP URL based expression usage 18d
- Critical CVE-2026-88776 Memory overflow vulnerability leading to unpredictable or erroneous behavior or Denial of Service 18d
- Critical CVE-2026-88775 Memory overflow vulnerability leading to unpredictable or erroneous behavior or Denial of Service 18d
- Critical CVE-2026-88777 Memory overflow vulnerability leading to unpredictable or erroneous behavior or Denial of Service 18d
- Critical CVE-2026-88773 HTTP Request Smuggling 18d
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No FIRST EPSS score.
- No fixed version, patch or mitigation documented.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-88778 is "TCP Initial Sequence Number (ISN) prediction", rated High. It affects Netscaler Application Delivery Controller (Citrix); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.5 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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